In drilling operations, the derrick is the structure designed to support and manipulate the drill string in and out of the well bore. The drill string is a series of drill pipe segments or joints detachably connected together. Typically, the drill pipe joints are coupled together to form a pipe stand consisting of two or three joints of pipe. The stands are then coupled together to form the drill string.
Drill collars and a drill bit are attached to a drill end of the drill string. The drill collars are heavier pipes having a larger diameter. They connect to the drill pipe and place weight on the drill bit such that the downward force from the weight of the drill string, drill collars, and drill pipe on the drill bit assists in the drilling process. As the drill bit and drill string rotate and penetrate into the well bore, additional lengths of pipe may be connected to the coupling end of the drill string. Each pipe segment or joint is typically thirty or forty five feet in length (Range 2-30 feet, Range 3-45 feet). The joints are coupled into double stands of approximately 60-65 feet or, for larger operations, triple stands (Range 2) of 90 feet.
Because the drill bit has to be changed after a few days or even a few hours, depending on the hardness of the matter being drilled through, the drill string must be tripped out of the hole frequently. This involves withdrawing the drill string from the well bore by conventional hoisting means such as a winch (draw works) mounted to the derrick or substructure, uncoupling the pipe stands of the drill string using a power wrench, rotary table, top drive or other torqueing and rotary machinery, and then standing the pipe stands in a conventional pipe storage or racking assembly such as a so-called racking board or finger board assembly. In larger operations, the drill string can weigh several hundred tones and requires an extremely powerful motor housed in the draw works to withdraw the drill string from the well bore. The pipe stands are then transmitted between the well bore, that is well center in the derrick, to and from the storage assembly. After replacing the bit, the pipe stands are removed from the storage assembly by the or derrickman and transported back to the well center where the pipe stands are re-coupled with the drill string and lowered back down the well bore to recommence drilling. Known as a “round trip”, this operation can take up to ten hours or more, depending on the depth of the well.
For decades, triple rigs have been used for drilling deeper holes than double rigs; triple rigs will not have fewer trips but there will be fewer connections between stands, and therefore less time is required to trip with a triple rig than a double rig for any particular depth. Further, a triple rig will hold ⅓ more pipe in the same size racking board and set back floor space as a double rig.
Present methods of manual tripping on both double and triple rigs require a person to stand on the racking board for the duration of the round trip, manually pulling back the stands or feeding the stands to the elevators so the stand can be lifted by the drawworks. This can be reasonably efficient when done by a skilled derrickman but, especially on a 10 or 12 hour round trip, it will be exhausting. This has been, and is presently, the predominant method of tripping on double and triple land rigs.
Automation of processes improves personnel safety and operating efficiencies. To automate the drilling and tripping processes, personnel must be removed from the rig floor and the racking board. In recent years there have been a number of mechanized products brought to market that remove personnel from the rig floor but racking of pipe while tripping has not changed—a person must still stand on the racking board for the time it takes to round trip.
The present invention eliminates the need for anyone to go up to the racking board while tripping pipe. Safety and efficiencies of the tripping process are thus improved.
Offshore drilling rigs have, for a number of years, used mechanized pipe racking systems. Equipment on offshore installations is permanently constructed on the drilling vessel. Offshore racking systems may weigh from 60,000 lbs to over 100,000 lbs and be capable of lifting 25,000 lbs. These systems are not practical for land drilling rigs.
Land rigs must be moved from one location to the next, every two or three weeks. Land drilling equipment is constructed to be readily rigged out, moved to the new location, and rigged up, quickly. A complete rig move may only take one to three days. What is missing in the prior art, and an object of the present invention to provide, is a relatively compact piece of equipment, with a total weight of less than 8,000 lbs, and capable of lifting 15,000 lbs; and which may be fitted onto both existing and new land drilling rigs. The present invention is also compact and robust. Whereas offshore systems are permanently installed and are capable of lifting only approximately one quarter of their own weight in tubulars, the present invention is portable and lifts nearly double its weight.
Also, it is an object of this invention to provide a smooth, controlled movement when moving the stands of drill pipe. When pipe stands are racked manually, there is considerable swinging of the bottom end of the stand when it is lifted with the drawworks. This swinging is slowed down by the rig floor personnel. This can put personnel at risk of injury. It is thus an object of the present invention to move stands in a controlled, smooth fashion, accelerating, moving, and decelerating to a stop with minimal swinging of the stand.
There are several devices and apparatus known in the art designed to improve the efficiency of the round trip operation. For example, U.S. Pat. No. 4,621,974 to Krueger, issued Nov. 11, 1986, provides an automated pipe equipment system for automatically removing pipe stands from, and adding pipe stands to, a drill string by using sensing means such as transducers to indicate to a programmable controller whether a pipe joint has been grasped by a racking arm. The Kruger system carries the stand of pipe in an assembly on the drill floor rather than lifting the stand. Furthermore, U.S. Pat. No. 4,117,941 to McCleskey Jr. et al., issued Oct. 3, 1978, provides a device which rapidly handles and vertically racks riser pipes and drill pipes in the drilling derrick. Manipulators effect the desired displacement of the pipes such that the lower ends of the pipes may rest on a set back platform on the drill floor and the upper ends of the pipes may be secured in a finger board. In addition, U.S. Pat. No. 4,013,178 to Brown et al., issued Mar. 22, 1977, provides a pipe racker wherein a maneuverable arm mounted on the derrick may grip the pipe joint anywhere along its length, lift the pipe, and move the pipe to another location without the need of a cable support. The vertical, horizontal and telescoping of the maneuverable arm provides the racker with three orthogonal degrees of freedom.
While the prior art provides devices for handling pipe stands in a more efficient manner, they do not provide a solution to address the instability associated with manipulating and transporting pipe stands that may exceed ninety feet in length and several thousand pounds in weight. Therefore, an unaddressed need exists in the industry to provide an apparatus for handling pipes in a stable and efficient manner to deal with deficiencies and inadequacies in the prior art.
In the prior art applicant is also aware of U.S. Pat. No. 6,821,071 which issued to Woolslayer et al. on Nov. 23, 2004, for an Automated Pipe Racking Process and Apparatus. Woolslayer describes a stand manipulator rather than a stand lifter automated pipe racking, wherein an arm support member is rotatable about an axis parallel to the well bore and wherein a gripper arm extends from the arm support member along an axis normal to the axis of rotation of the arm support member. A gripper head on the gripper arm extends from the gripper arm to grip the upper end of a pipe stand. The arm assembly is suspended from a carriage which moves along the underside of a working board mounted to a finger board or racking board. The working board extends between sets of fingers. Rotation of the arm and movement of the carriage permits movement of the upper end of a pipe stand from the well bore to the slots between the fingers. The lower end of each pipe stand is moved manually onto a base grid adding rows of multiple cells. When a pipe stand is on a cell it acts as a switch to send a control signal, upon which control signal the carriage, arm support member, gripper arm, and gripper head on the gripper arm engage the top of the pipe stand. A proximity sensor verifies that the pipe stand is in the gripper assembly. With the lower end of the pipe stand manually moved over one of the cells and the pipe stand than lowered onto that cell on the grid, the upper end of the pipe stand is than moved into a slot between the fingers of the racking assembly.
Thus Woolslayer teaches merely guiding the top of the pipe stand after the pipe has been lifted by the drilling rig elevators. In other words, the pipe stand itself is not lifted by the Woolslayer articulated arm. In the present invention, it is an object to provide an articulated assembly which lifts a complete pipe stand and is capable of lifting in the order of 12,000-15,000 pounds in contradistinction to the 1,000 lbs contemplated by Woolslayer, and once lifted carrying the completed pipe stand in a vertical position and inserting the pipe stand still in its vertical position into a desired slot between fingers of the racking board.